I work for a product company and some of our documents are translated from English to Spanish. I noticed that the translator had translated Latin abbreviations like 'i.e.' and 'e.g.' to Spanish as 'es ...

I think this question may involve more than Spanish, and may include Romance languages or even Latin.
I wonder why, when, and how did vowels E and I get special treatment from consonants like C, G, ...

Many (most? all?) Spanish words containing the letter h come from corresponding Latin words containing the letter f. Through what process did /f/ get softened to /h/? During what time period did this ...